Injector for fuel

ABSTRACT

A fuel injector comprises a body having a jet at one extremity thereof, which jet has an orifice for the discharge of a fuel from the jet. A needle is slidable within the jet for controlling the flow of fuel from the orifice. One end of the needle is acted upon by a fluid under pressure contained in a chamber connected to a pressure source. The fluid biases the needle towards a seating for closing the orifice. When an engine, to which the fuel injector is mounted, is started, fuel under pressure engages a face of the needle such that the needle is raised from its seating against the biasing effect of the liquid under pressure so that fuel escapes through the orifice.

United States Patent Guegan et al.

[ 1 Sept. 5, 1972 [54] INJECTOR FOR FUEL [72] Inventors: Yves Guegan, Lille; Maurice Tacquet, Marcq en Baroeul, both of France [73] Assignee: Crepelle and Cie, Lille, France [22] Filed: Sept. 8, 1970 21 Appl. No.: 70,448

[30] Foreign Application Priority Data Sept. 15, 1969 France. ..6931320 [52] US. Cl. ..239/94, 239/95, 239/533 [51] Int. Cl ..F02m 45/10 [58] Field of Search ..239/93, 94, 95, 533

[56] References Cited UNITED STATES PATENTS 1,843,410 2/ 1932 Von Salis ..239/94 X 2,283,725 5/1942 Eichelberg ..239/533 UX 3,352,245 11/1967 Wolfi" ..239/93 X 2,150,574 3/1939 Amery ..239/95 2,173,812 9/1939 Bischof ..239/93 X 2,173,813 9/1939 Bischof ..239/93 UX 2,458,294 l/ 1949 Parker ..239/95 X 2,559,364 7/ 1951 Mashinter ..239/93 X I 3,282,512 11/1966 Bluhm et al. ..239/533 3,409,226 1 l/ 1968 Steiger ..239/94 Primary Examiner-Lloyd L. King Assistant ExaminerReinhold W. Thieme Att0rneyRobert E. Burns and Emmanuel J. Lobato ABSTRACT A fuel injector comprises a body having a jet at one extremity thereof, which jet has an orifice for the discharge of a fuel from the jet. A needle is slidable within the jet for controlling the flow of fuel from the orifice. One end of the needle is acted upon by a fluid under pressure contained in a chamber connected to a pressure source. The fluid biases the needle towards a seating for closing the orifice. When an engine, to which the fuel injector is mounted, is started, fuel under pressure engages a face of the needle such that the needle is raised from its seating against the biasing effect of the liquid under pressure so that fuel escapes through the orifice.

6 Claims, 2 Drawing Figures INJECTOR FOR FUEL BACKGROUND OF THE INVENTION.

The present invention relates to injectors for the vapourization of fuel, and in particular to fuel injectors for internal combustion engines.

In most known fuel injectors, the flow of fuel through an orifice in a jet is controlled by a needle. The lifting of the needle from a cooperating seating is limited by a mechanical stop and, as a result, a damaging shock is applied to the needle when the needle engages the stop. The known injectors often have a rated helicoidal compression spring for imparting a thrust to the needle and rapid deterioration of this spring and wear on the seating and on the needle have a serious effect on the accuracy of the calibration of the injector and, as a result, on the quality of the vapourization.

Moreover, the known injectors operated by a spring require a collector for the inevitable leakage of fuel along the needle.

More recently, injectors have appeared (for example, see United Kingdom Pat. No. 566,692) in which the spring is replaced by a liquid under pressure, acting directly on the end of a needle to control its engagement of a mechanical stop. These injectors function fully, or not at all, in the manner of a valve, and as a result, the needle suddenly strikes the cooperating seating which rapidly deteriorates the corked seatings. Furthermore, this question of the force of the impact of this needle on the seating prevents the utilization of injectors having a large flow and thus, the production of engines of higher power having a high rotational speed.

Further, in the case of pressure variations in the fuel supply systems, a regular, uncontrolled movement of the needle is observed.

Such injectors with needles acted upon by a liquid under pressure are, moreover, described, in French Pat. No. 959,196, in which the rating of the injector is obtained by the pressure of a liquid above the needle without using the compressability of the liquid in order to limit the travel; thus, moreover, the fuel itself which is conducted above the needle by means of an narrow channel which creates a loss in the load.

German Pat. No. 827,140 describes an injector in which the needle comes up against a mechanical stop during its mounting, from where it is permitted, by the liquid, which is found, also, to be the fuel led by a laminar tunnel in such a way as to create a'de-phasing of the pressure.

A device which can be classified between the needle injector operated by a spring and the needle injector operated by liquid, is described in U .8. Pat. No. 3 ,282,5 1 2. The usual helicoidal spring is replaced by an hermetically closed bellow filled with liquid and the needle and its mobile unit, constituted by a hollow steel body fixed to the needle and filled with liquid in communication with the bellows is displaced up to a mechanical stop. All these cited drawbacks are in existence; loss of fuel, unit being too heavy, mechanical stop above the mobile units deteriorating, seating subjected to the needle impact when suddenly returned.

AIMS OF THE INVENTION.

An object of the present invention is the provision of an injector for fuel having a movable needle, the movement of which needle from a cooperating seating is not limited by a mechanical stop but by a fluid stop and the displacements of which needle are shock absorbed.

According to the present invention, an injector for fuel, comprising a jet having an orifice, a needle within the jet for controlling the flow of fuel through the orifree, the needle being movable between a first position, in which the needle engages a seating for preventing the flow of fuel through the orifice, and a second position, in which the needle is spaced from the seating, the needle having two opposed surfaces, a first of which surfaces is exposable to pressure from a fluid for biasing the needle towards the first position, and the second of which surfaces is exposable to pressure from the fuel for biasing the needle towards the second position.

Preferably, the first surface forms the end face of the needle remote from the seating, and defines with a portion of a bore in which the needle is slidable, a chamber, the chamber being in communication with a source of liquid under pressure and containing a con- DESCRIPTION OF THE FIGURES.

An embodiment of the invention will now be described, by way of example, reference being made to the Figures of the accompanying drawings in which:

FIG. 1 is an axial cross-section of an injector for fuel mounted on an engine; and

FIG. 2 is a detail to a larger scale of the injector of FIG. 1.

DESCRIPTION OF A PREFERRED EMBODIMENT.

As shown, injector 1 is mounted on the upper part of a cylinder 2 of an internal combustion engine, opposite a piston 3.

The injector 1 comprises a body 4 at the lower part of which is fixed a vapourization jet 5 in which is mounted, axially slidable, an injection needle 6. The needle 6 is normally pressed against seating 7, bored with orifices 8 for the injection of the fuel into the combustion chamber of cylinder 2.

In the body 4 and the vapourizing jet 5, a channel 9 is bored which opens out into a cavity 10 made in the vapourizing jet 5 and through which passes the needle 6. Above this cavity 10, the needle 6 has a section 6a of greater diameter than that of the lower part of needle 6, which section 6a forms a piston. The section 6a slides in an upper bored cylinder 11 of a corresponding diameter, formed in the vapourizing jet 5.

It should be noticed, that the section 6a has a shaped part 6b facilitating the gripping of the needle 6.

The channel 9 is connected by a duct 12 to a fuel injection pump 13. Needle 6 is freely mounted in the vapourizing jet 5 and above the upper end 60 of the needle a chamber 14 is formed which chamber 16 communicates with an axial duct 16 via a non-return valve 15.

The non-return valve 15 is arranged at the lower end of an axial duct 16 formed in the body of the injector and is normally closed by a spring 17 connected to one side of the non-return valve 15, to pull it upwards and to maintain it on its seating. The other end of the spring 17 is connected to the inside end of a threaded member 18. The member 18 is formed with a channel, which communicates with a duct 19. At the opposite end of duct 19 is a pump 20 the inlet of which communicates with a reservoir 21 containing a regulating liquid. A pressure regulator 22 is connected to the duct 19,

which ensures the return of the regulating liquid to the reservoir 21.

A part of the regulatin g liquid runs, as will be more precisely described further on, through the length of needle 6 and is mixed with the fuel, the liquid can be chosen from among combustible products, such as petroleum oil, oil, petrol, or even a fuel of the same type as used by the engine in order to prevent any deterioration of combustion.

Body 4 of injector 1 has an air vent orifice 23 at its upper part, communicating by duct 24, with the axial duct 16.

The injector 1 functions in the following manner:

Pump 20, which is rotatably driven either by the internal combustion engine or by .an auxiliary motor, sends the regulating liquid via duct 19 into the axial duct 16 and, through the non-return valve 15, into chamber 14. As a result, the lifting of needle 6 is limited by the compressibility of the liquid contained in the upper chamber 14. Liquid thus contained, acts as a compensating spring or a hydraulic stop.

When the engine is functioning, the injection pump 13 is driven and the fuel is fed under high pressure into the duct 12 and the duct 9 up cavity 10 of the vapourizing jet 5. With the force of the pressure of the liquid fuel in cavity 10, needle 6 is pushed upwards against the hydraulic stop 14, with a result that the section 6a acts as a piston and the lower extremity of the needle 6 therefore leaves the seating 7, enabling the injection of the fuel through orifice 8. At the end of the travel of the floating needle 6, the latter is found in its position of equilibrium.

The displacement of the needle 6 is in proportion to the pressure of the injection. As soon as this injection pressure diminishes, the needle 6 drops back again into the direction of the seating 7 and the impact speed of the needle 6, when closing, is very slight. As a result, the risk of damaging the seating 7, a drawback which is encountered in known injectors, is avoided. The risk of which is also reduced by reason of the fact that the volume of needle 6 is clearly less than that of the needle and the moving parts of known injectors.

Adjustment of the pressure of the regulating liquid fed by pump 20, by means of regulators 22, enables the pressure of fuel 29 fed through duct 9 to be varied, while needle 6 comes away from seating 7. If the opposing pressure in the chamber 14 has a high value, the opening pressure is also as high and thus the springing back of needle 6 which can follow a variation of pressure in duct 12, can be avoided.

Generally, pressure of the regulating liquid is maintained in chamber 14 at a higher value than that of the maximum pressure of combustion and therefore, no combustion gases can'come up along needle 6.

Furthermore, as the pressure of the liquid so forming the hydraulic stop in chamber 14 is also greater then the residual pressure in the injection duct 9, apart from injection period, the regulating liquid of hydraulic stop 14 leaks towards the cavity 10, along needle 6 which assures the lubrication and the cooling of the needle.

Pressure regulator 22 enables the pressure of the liquid constituting the hydraulic stop 14 to be varied during the functioning of the motor and according to the conditions of use of the latter. Normally, this adjustment is made once and for all, by rating of the spring 17. However, it is possible for automatic regulating according to the speeds of the motor in relation to the fuel supply.

The opening and closing pressure of the various injectors connected to the same pump 13 are stable and identical between the various injectors which are subjected to the same pressure by reason of the fact that all the injectors are connected to the same channel 19 by which the liquid forming the hydraulic stop is provided.

What is claimed is:

1. An injector for fuel comprising an elongate body, a jet forming passage arranged in the body at one extremity thereof and having an orifice, a needle within the jet forming passage for controlling the flow of fuel through the orifice, the needle being movable between a first position in which the needle engages a cooperating seat for preventing the flow of fuel through the orifice, and a second position in which the needle is spaced from the seat, the needle being formed along a portion of its length, as a piston, slidable within a cylinder formed in the jet forming passage, a first surface of the piston being exposable to pressure from a liquid for biasing the needle towards the first position, and a second surface of the piston being exposable to pressure from the fuel for biasing the needle towards the second position, a non-return valve arranged in a surface of the cylinder opposite the first surface, a

chamber defined by said first surface and the walls of said cylinder, the non-return valve permitting the flow of liquid from a source of liquid under pressure into said chamber, and means for applying said source of liquid under pressure to said chamber for maintaining the latter at a constant pressure.

2. An injector according to claim 1, wherein the nonreturn valve is mounted at one extremity of a duct formed in the body of the injector and connected by a conduit to the source of liquid under pressure, the nonreturn valve being urged toward the closed position by a spring in the duct. I

3. An injector according to claim 2, wherein the source of liquid under pressure communicates with a pump connected to the conduit to which a pressure regulator is connected.

4. An injector according to claim 1, wherein the pressure of the liquid in the chamber is higher than the maximum combustion pressure in the cylinder of an engine to which the injector is operatively attached.

5. An injector according to claim 1, wherein the pressure of the liquid in the chamber is higher than the residual pressure of the fuel at the end of the injection of the fuel into an inlet duct in the body and the jet communicating with the second surface.

6. An injector according to claim 2, wherein a pressure regulator is connected to the conduit, the regulator being adjustable during functioning of an engine to which the injector is operatively attached. 

1. An injector for fuel comprising an elongate body, a jet forming passage arranged in the body at one extremity thereof and having an orifice, a needle within the jet forming passage for controlling the flow of fuel through the orifice, the needle being movable between a first position in which the needle engages a cooperating seat for preventing the flow of fuel through the orifice, and a second position in which the needle is spaced from the seat, the needle being formed along a portion of its length, as a piston, slidable within a cylinder formed in the jet forming passage, a first surface of the piston being exposable to pressure from a liquid for biasing the needle towards the first position, and a second surface of the piston being exposable to pressure from the fuel for biasing the needle towards the second position, a non-return valve arranged in a surface of the cylinder opposite the first surface, a chamber defined by said first surface and the walls of said cylinder, the non-return valve permitting the flow of liquid from a source of liquid under pressure into said chamber, and means for applying said source of liquid under pressure to said chamber for maintaining the latter at a constant pressure.
 2. An injector according to claim 1, wherein the non-return valve is mounted at one extremity of a duct formed in the body of the injector and connected by a conduit to the source of liquid under pressure, the non-return valve being urged toward the closed position by a spring in the duct.
 3. An injector according to claim 2, wherein the source of liquid under pressure communicates with a pump connected to the conduit to which a pressure regulator is connected.
 4. An injector according to claim 1, wherein the pressure of the liquid in the chamber is higher than the maximum combustion pressure in the cylinder of an engine to which the injector is operatively attached.
 5. An injector according to claim 1, wherein the pressure of the liquid in the chamber is higher than the residual pressure of the fuel at the end of the injection of the fuel into an inlet duct in the body and the jet communicating with the second surface.
 6. An injector according to claim 2, wherein a pressure regulator is connected to the conduit, the regulator being adjustable during functioning of an engine to which the injector is operatively attached. 